Outcome Analysis of the use of Allografts in Spine Fusion Surgery

INTRODUCTION: Since time immemorial, replacement of man’s organs have always found fascination amongst us. And among all replacements bone transplantations are the most widely performed. “Bone is the most commonly transplanted tissue in the body than any other tissue or organ except blood”. Transplanted bone, tendon and ligaments are used extensively in orthopedics, neurosurgery, dental surgery and plastic surgery for procedures including repair of fractures and damage caused by illness and injury. . The application and the scope of allografts are the most in orthopaedics. Allograft have been proved to be useful in massive defects, spinal fusions, large joint defects and reconstructive of bone tumors in spite of several short timings. Allografts have further extended the reconstruction abilities of surgeon and provide innovative option for biologic reconstruction with less patient morbidity. AIM: To evaluate the rates of fusion of allografts and the analysis of their outcome in various spine fusion surgeries. MATERIALS AND METHODS: The materials for this study was based on a prospective study conducted at the Department of Orthopaedics and Traumatology, Government General Hospital, Chennai from May 2006 till November 2008. Inclusion Criteria are 1. All vertebral fractures & fracture dislocations requiring stabilisation, 2. Spondylolysis, 3. Spondylolisthesis patients, 4. Caries spine, 5. Kyphoscoliosis correction. Exclusion criteria are 1. Age >55 yrs, 2. chronic nicotine users, 3. diabetes mellitus, 4. presence of any other co-morbid conditions affecting the microvasculature thereby influencing the rates of fusion. RESULTS: Grade 2 fusion levels were considered as reasonably enough to take the load shared by the implant off. This level of fusion was achieved in 10 cases. Grade one fusion was seen in one case. In order to compare the fusion rates with autograft added for osteo-induction 3 patients were embedded with auto – allograft mixture . They showed gr 2 fusion at 9m. Two cases of graft resorption were seen in those without implants or with improper, unstable fixation.One patient (L5S1 listhesis) had no implants, with decompression and in situ allografting. Though patient is symptom free, there was complete resorption of the allograft on the follow up CT at 16 months. In one case( Case 18) of spondylolisthesis allograft were packed on the rt side with autograft on the left side. At 7 months follow up there was Grade 2 fusion at the autograft side while the allograft side showed Gr 3 patchy fusion, thereby demonstrating the slower fusion rates with allografts. The mean period for achieving gr 2 fusion was 12 months. There were no allograft associated complications like: • Post op wound infection, • Graft rejection reactions.( manifesting as sterile discharges), • Transmission of diseases. CONCLUSION: Bone autografting remains the most effective grafting material as it provides all the 4 essentials of bone regeneration. However the shortcomings of large harvesting and its associated morbidity provides us the scope for other alternatives. Among these alternatives allografts are the most inexpensive, most readily available option. The attainment of solid bone fusion is multifactorial. There is a race between bone resorption and new formation in seeking to create a new fusion mass which can withstand mechanical loads. The following are the various conclusions regarding the multiple factors that governed allograft fusion in this study. Deep Frozen Irradiated allografts have the maximum retention of their strength and structure. There was NO infection during the use of these Irradiated allografts. In anterior fusion the allograft, especially cortical bone of the femoral ring, required a considerable time before the full incorporation of the graft would take place. It appeared that at least 18 months is required before the majority of the grafts would be fully incorporated to the host bone